Taste disorders are common in older people, being able to suffer alterations or losses of the ability to identify sweet, salty, bitter, sour and umami tastes. At the epidemiological level, taste changes are classified into three diagnostic categories: ageusia (loss of the sense of taste), hypogeusia (diminished gustatory capacity) and dysgeusia (distortion of the sense of taste). These taste deficiencies are caused by the aging process of the sensory system (50%), physiological changes due to medications (21.7%), zinc deficiency (14.5%), oral diseases (7.4%), such as dental caries, gingival and periodontal diseases, and finally systemic diseases (6.4%).

With respect to aging, the loss of taste is understandably associated with physiological changes, such as narrowing and dryness of the oral mucosa due to decreased keratinazation and a thinning of the epithelial structure. In addition, the density of the taste buds decreases. On the other hand, systemic diseases are multifactorial, which introduces greater variability. Loss of taste associated with pathologies of the central nervous system can be found, for example when elderly patients suffer an ischemic stroke or Parkinson’s disease. Regarding endocrine alterations, hypogeusia is quite common in diabetic patients. With respect to cancer, hypogeusia usually appears in patients with lung cancer (65%) as well as breast, head and neck cancers (88-93%). Concerning renal, hepatic and cardiovascular pathologies, a consensus on a possible correlation between hypertension and greater sensitivity in the sense of salty taste has not been found. Finally, hypogeusia is diagnosed in 70% of patients with Sjögren’s syndrome (affecting the gastrointestinal tract), in rheumatic disorders, as well as respiratory and viral diseases.

The importance of taste disorders produced by prescribed drugs for cardiovascular diseases should also be taken into account. These include diuretics, beta-adrenergic blockers, antiarrhythmics, ibuprofen or diclofenac. These last two cause bitter, salty or sour taste sensations. Psychotropic drugs and antibacterial agents (for example penicillins) cause taste disorders, which can induce zinc and copper deficiencies. The antidiabetic drug biguanide causes a metallic taste in the mouth. On the other hand, the sensory alterations produced by treatments such as chemotherapy, radiotherapy and surgery also stand out. Finally, the lifestyle-induced disorders, such as poor hygiene, abusive alcohol consumption and smoking, should be considered. Although it is still unclear whether these activities fully interfere in the gustatory sense, there are studies, such as Haeing’s, which indicate that smokers have a higher threshold for bitter tastes at the tip of their tongue, while Nilsson reported that the threshold for salty flavors was higher on the soft palate.

If there is no sensory-depriving pathology present, then generally decreased sensory capacity is not detected until the fifth decade of life, with a more pronounced degeneration in males. The thresholds for detecting sour, salty and bitter flavors increase with age, whereas for sweet tastes the threshold doesn’t seem to be related to age. However, the decreasing perception of salty flavors may induce older people to season their food with excessive amounts of salt, which can increase the risk for cardiovascular and cerebrovascular diseases, worsening of the glycemic profile, higher mortality in diabetics, greater risk of osteoporosis and, finally, increased risk of gastric cancer.

Older people tend to prefer sugary foods. A decrease in the perception of taste may provoke an increase in sugar doses in beverages and foods, causing an increased risk of hyperglycemia in diabetics, or hypertension in normotensives. It can also cause a worsening of the blood pressure profile in hypertensive patients or weight gain in obese patients. Regarding the perception of the sour taste, recognition thresholds are higher in men and women in the eighth decade of life and in the elderly who frequently consume medications. The decrease in this perception may mean an increase in the consumption of acidic foods and condiments (citrus and vinegar respectively) producing changes in gastric acidity, among other aspects. Similarly, the decrease in bitter taste may increase the risk of ingesting spoiled food. Finally, the decrease in the perception of umami taste can cause hyposalivation, weight loss, malnutrition and reduced quality of life.